EP 0731957 B1 19971015 - METHOD FOR SCALING AND FILTERING IMAGES USING DISCRETE COSINE TRANSFORMS
Title (en)
METHOD FOR SCALING AND FILTERING IMAGES USING DISCRETE COSINE TRANSFORMS
Title (de)
VERFAHREN ZUR BILDSKALIERUNG UND ZUM FILTERN MIT DISKRETER COSINUSTRANSFORMATION
Title (fr)
PROCEDE DE MISE A L'ECHELLE ET DE FILTRAGE D'IMAGES AU MOYEN DE LA TRANSFORMEE EN COSINUS DISCRETE
Publication
Application
Priority
- US 9413617 W 19941129
- US 15979593 A 19931130
Abstract (en)
[origin: WO9515538A1] Image processing method and apparatus by which images in the spatial domain can be represented in the frequency domain through the use of discrete cosine transforms, conveniently operated on to achieve scaling and filtering effects while in the frequency domain, and then retransformed to the spatial domain or stored, displayed, reproduced or transmitted to distant locations for subsequent reuse. The scaling techniques which the invention utilizes can be for image enlargement by interpolation or image reduction by decimation. In the case of decimation, a filtering operation preferably is first performed in the frequency domain to avoid artifacts in the decimation process. The filtering operation is mathematically equivalent to a linear convolution in the spatial domain as a consequence of the properties of the DCT transformation. In both interpolation and decimation procedures, use is made of a hybrid inverse discrete cosine transform in which the argument of the series of cosine terms are evaluated at values arrived at by scaling ratio considerations, rather than the usual sampling index increments. As a consequence, image points other than original image data in the spatial domain can be created or replaced by an approximation technique which involves representing them in frequency space by a series of terms that can be considered to be continuous over the range of the sampling index corresponding to that of the original image data.
IPC 1-7
IPC 8 full level
H04N 5/262 (2006.01); G06F 17/14 (2006.01); G06T 3/40 (2006.01); G06T 5/00 (2006.01); G06T 5/20 (2006.01); G06T 9/00 (2006.01); H04N 7/26 (2006.01); H04N 7/30 (2006.01); H04N 7/46 (2006.01); H04N 9/04 (2006.01)
CPC (source: EP KR US)
G06F 17/147 (2013.01 - EP US); G06T 3/40 (2013.01 - KR); G06T 3/4084 (2013.01 - EP US); H04N 19/132 (2014.11 - EP US); H04N 19/176 (2014.11 - EP US); H04N 19/18 (2014.11 - EP US); H04N 19/48 (2014.11 - EP US); H04N 19/59 (2014.11 - EP US); H04N 19/60 (2014.11 - EP US); H04N 19/90 (2014.11 - EP US); H04N 2209/046 (2013.01 - EP US)
Designated contracting state (EPC)
AT BE DE DK ES FR GB IE IT NL
DOCDB simple family (publication)
WO 9515538 A1 19950608; AT E159366 T1 19971115; CA 2171335 A1 19950608; DE 69406306 D1 19971120; DE 69406306 T2 19980129; EP 0731957 A1 19960918; EP 0731957 B1 19971015; JP H09506193 A 19970617; KR 960706148 A 19961108; US 5740284 A 19980414
DOCDB simple family (application)
US 9413617 W 19941129; AT 95903160 T 19941129; CA 2171335 A 19941129; DE 69406306 T 19941129; EP 95903160 A 19941129; JP 51568995 A 19941129; KR 19960702069 A 19960422; US 42745795 A 19950518